Nonlinear Phenomena in Photonic Nanostructures: Modulational Instabilities And Solitons

Xuesong Zhao

Research output: ThesisDoctoral Thesis

Abstract

This thesis discusses nonlinear effects, such as modulation instability and solitons in
nano-structured waveguides. The nanoscale optical waveguides have extremely small
transverse dimensions, which can provide tight confinement of light. Therefore, by
changing the waveguide geometry, the waveguide dispersion can be strongly altered. On
the other hand, the confinement also enhances the nonlinear dispersion, allowing for
nonlinear optical phenomena supported by dispersion of nonlinearity.
The new models governing evolution of the amplitudes of components of the optical
waves interacting in the waveguides are derived for continuous wave and pulse wave
using perturbation expansion method. The new modulation instability condition is found,
as we take into account the dispersion of nonlinearity which is enhanced through a strong
variation of the modal profile with the wavelength of light in sub-wavelength waveguides.
We demonstrate that this dispersion of nonlinearity can lead to the modulation instability
in the regime of normal group velocity dispersion through the mechanism independent
from higher order dispersions of linear waves for continuous wave. We address that the
new mechanism highly associated with dispersion of nonlinearity in sub-wavelength
semiconductor waveguide induces the modulation instability in picsecond regime together
with the cascaded generation of higher-order sidebands. The impact of the dispersion of
nonlinearity on spectral broadening of short pulses in a silicon waveguide also is
considered.
We study the temporal evolutions of fundamental and one-ring solitary waves with phase
dislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numerically
analyze the properties of these nonlinear localized modes and, In particular, reveal
different scenarios of their instability.
LanguageEnglish
QualificationPh.D.
Awarding Institution
  • University of Bath
Supervisors/Advisors
  • Skryabin, Dmitry, Supervisor
Award date23 Apr 2014
StatusUnpublished - Nov 2013

Fingerprint

solitary waves
photonics
waveguides
nonlinearity
modulation
continuous radiation
wavelengths
dielectric waveguides
theses
pulses
sidebands
group velocity
optical waveguides
perturbation
expansion
rings
symmetry
silicon
profiles
geometry

Keywords

  • Nonlinear optics

Cite this

Nonlinear Phenomena in Photonic Nanostructures : Modulational Instabilities And Solitons. / Zhao, Xuesong.

2013. 155 p.

Research output: ThesisDoctoral Thesis

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N2 - This thesis discusses nonlinear effects, such as modulation instability and solitons innano-structured waveguides. The nanoscale optical waveguides have extremely smalltransverse dimensions, which can provide tight confinement of light. Therefore, bychanging the waveguide geometry, the waveguide dispersion can be strongly altered. Onthe other hand, the confinement also enhances the nonlinear dispersion, allowing fornonlinear optical phenomena supported by dispersion of nonlinearity.The new models governing evolution of the amplitudes of components of the opticalwaves interacting in the waveguides are derived for continuous wave and pulse waveusing perturbation expansion method. The new modulation instability condition is found,as we take into account the dispersion of nonlinearity which is enhanced through a strongvariation of the modal profile with the wavelength of light in sub-wavelength waveguides.We demonstrate that this dispersion of nonlinearity can lead to the modulation instabilityin the regime of normal group velocity dispersion through the mechanism independentfrom higher order dispersions of linear waves for continuous wave. We address that thenew mechanism highly associated with dispersion of nonlinearity in sub-wavelengthsemiconductor waveguide induces the modulation instability in picsecond regime togetherwith the cascaded generation of higher-order sidebands. The impact of the dispersion ofnonlinearity on spectral broadening of short pulses in a silicon waveguide also isconsidered.We study the temporal evolutions of fundamental and one-ring solitary waves with phasedislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numericallyanalyze the properties of these nonlinear localized modes and, In particular, revealdifferent scenarios of their instability.

AB - This thesis discusses nonlinear effects, such as modulation instability and solitons innano-structured waveguides. The nanoscale optical waveguides have extremely smalltransverse dimensions, which can provide tight confinement of light. Therefore, bychanging the waveguide geometry, the waveguide dispersion can be strongly altered. Onthe other hand, the confinement also enhances the nonlinear dispersion, allowing fornonlinear optical phenomena supported by dispersion of nonlinearity.The new models governing evolution of the amplitudes of components of the opticalwaves interacting in the waveguides are derived for continuous wave and pulse waveusing perturbation expansion method. The new modulation instability condition is found,as we take into account the dispersion of nonlinearity which is enhanced through a strongvariation of the modal profile with the wavelength of light in sub-wavelength waveguides.We demonstrate that this dispersion of nonlinearity can lead to the modulation instabilityin the regime of normal group velocity dispersion through the mechanism independentfrom higher order dispersions of linear waves for continuous wave. We address that thenew mechanism highly associated with dispersion of nonlinearity in sub-wavelengthsemiconductor waveguide induces the modulation instability in picsecond regime togetherwith the cascaded generation of higher-order sidebands. The impact of the dispersion ofnonlinearity on spectral broadening of short pulses in a silicon waveguide also isconsidered.We study the temporal evolutions of fundamental and one-ring solitary waves with phasedislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numericallyanalyze the properties of these nonlinear localized modes and, In particular, revealdifferent scenarios of their instability.

KW - Nonlinear optics

M3 - Doctoral Thesis

ER -